Activated carbon or charcoal (AC) with a high adsorptive surface & pore volume for oral administration is a good candidate for treating different pathological states accompanied by inflammation. The biocompatibility of such ACs in vivo is evaluated by studying the total body weight dynamic, occurrence of tumors, and morphology of organs in rats fed with this AC. HSGD granulated (derived from N-containing synthetic polymers, Ukraine), and CA-M (derived from apple wood, handy milled, Moldova). Both ACs were obtained by the method of steam activation in the fluidized bed of the laboratory furnace. AC samples were evaluated using low-temperature nitrogen adsorption and the adsorption of albumin-bound toxins (unconjugated bilirubin) [1]. 45 Wistar female rats 2 months old were allocated into 3 groups: HSGD, CA-M, and Control. The daily dose of ACs was 1.2 g per 1 kg of the rat’s body weight over the course of 10 days every 2 months, mixed in a small amount of food [2] during 14 months (in 9 rats-histology) and till death in other 36 rats. Animals were weighed, and visually examined for tumor occurrence, and 3 animals from each group 14 months after the start of the experiment were sacrificed and organ tissues were carefully isolated for histological examination [2]. Table 1 presents the results of nitrogen adsorption by ACs (BET surface and total pore volume) as well as the quantity of unconjugated bilirubin adsorbed by AC from the albumin solution. These results indicate the high adsorptive capacity of both ACs in comparison with existing commercial analog eg. (Kremezin, AST—120- 1600 m2/g). Table 1. Activated carbon (AC) BET surface, m2/g V mesopores, (cm3/g) Adsorbed albumin-bound bilirubin (mg/per 1 g of AC) HSGD 2667 3.15 36.4 CA-M 1857 0.84 30.4 No statistical difference in total body weight dynamic, in the percentage of visually detected spontaneous tumors and the average age of tumor, was found in both AC groups in comparison with the Control (Table 2). Table 2. Groups of rats Total duration of AC administration (days) Total body weight (g) % of detected tumors The average age of tumor (months) Before Experiment 9 months after 18 months after HSGD (n=15) ~115 155±11 296±31 356±38 29 22 CA-M ( n=15) ~115-120 159±7 292±23 330±46 40 27 Control (n=15) 0 160±5 295±19 333±38 43 25 Histological examination of kidneys, liver, thymus, heart, spleen, stomach, lunge, small intestine, and colon reveals after 70 days of AC administration any difference with those of Control. These preliminary results indicate the signs of good biocompatibility of both highly-activated ACs long-time administered orally in relatively high doses.